The overall objective is to study how single binocular vision is achieved in humans with normal and with binocularly deficient visual systems, with a particular emphasis placed on the contribution of peripheral retinal regions to the mediation of fusional response. To that end, it is proposed to: 1. Investigate the possibility and nature of sensory interactions among neighboring retinal regions during fusional compensation. 2. obtain comparative data on the nature of peripheral fusional response in the presence of different types of central visual field defects. We propose to measure the fusional response to wide-angle fusional stimulation of patients with adult-onset macular degeneration and compare their response to that of monofixators and normal subjects with artificial bilateral scotomas.